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2006 Forester X 2.5 AT Auto
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Discussion Starter #1 (Edited)
Because of the jobs I've had, I've driven a company-owned truck home for the last several years. However, due to a recent job change, I had to be buy a second vehicle, and ended up with my '06 Forester. Now, I get to do something I haven't been able to for a long while-perform incremental maintenance on a high-mileage vehicle and track how much mileage can be gained by each action. I've done this with F-150s, Chrysler minivans, and even a Javelin. I'm going to update this thread as I do each each thing and record the mileage increases. First, a little background about my automotive experience to maybe lend some explanation as to why I will be using certain products/taking certain steps:

-I was a salesman and tech adviser at Summit Racing Equipment for several years. This experience exposed me to many different products/brands/customer experiences. I got to find out what worked/didn't work, and which claims of certain product manufacturers seemed to pan out and which seemed to be bogus. So, I definitely have my favorite brands and products within a brand line, and have a good idea on what is a waste of money.

-Since 1986, I've owned and driven a more vehicles that I can remember, and have owned many beaters that I've had to keep going and wrench the last possible drop of mileage out of, so I've gotten pretty good at it.

About the car:

-2006 Forester, 2.5 N/A, A/T 144,400 ml. Very good condition. I can tell it was well taken care of, but have no maintenance records, except that the timing belt/water pump was replaced at 80,000 ml. Purchased at a reputable used car lot that had purchased from auction. Owner's manual packet shows it was originally purchase locally, and is remarkable rust free, despite being a Northern Ohio car from new.

-During the test drive, both the lot owner and I noticed a coolant smell when we got off the highway. His mech found a leaking hose, replaced, then I purchased the car for $3900. The next day (before I picked it up), the lot owner drove it to make sure there were no other issues, and he could still smell hot coolant. Further inspection found coolant leaking from the inside out on the pass side head gasket. Oil showed no signs of coolant, which was good. He took it to a local Subaru tech, and paid for head gasket replacement (both, of course) and machine-shop cleanup of heads/bowls/valves (I was provided with pics). The mech told me he was very impressed with the post-repair compression checks, which indicated that the oil was changed regularly and there is no abnormal piston-ring wear/valve seal issues. Mind you, I had already paid for the car and had signed the as/is, no warranty document, but the dealer still paid for 100% of this, including going ahead and doing the timing belt/water pump again since the engine was out and opened up. He even gave me a loaner until my car was ready-like I said, very reputable used-car lot.

-So, I'm starting with a good-running vehicle with fresh head gaskets, oil and coolant change, timing belt/WP, and a new Fram air filter, and great compression. However, plugs and wires of unknown age and condition, and no idea when/if the trans or diffs have had fluids changed. In short, a perfect specimen for my experiment.

-Since the repair, I've ran three full tanks of gas through it to get a good baseline mileage. My average right now, with no work yet done by me, is 25.4 MPG. We use the family truckster minivan on the weekends, so all of my driving is to and from work, 64 miles per day round trip. 56 of this is highway, and 8 is suburban/rural, with 2 stop signs and 3 lights total. I've been getting gas from the same gas station every time, and will continue to do so for the sake of experimental control.

-The first thing I'm doing is spark plugs and wires, which arrived today, and will do this weekend, weather permitting (lots of rain forecasted, and I'll be working outside). My goal is to do 2 full tanks after each maintenance activity in order to get a good MPG average before moving on to the next maintenance activity. This will be a long-tern experiment. I'll also be keeping track of how much money I'll be spending vs. MPG gained, to see how long it takes to recover the cost of the parts in mileage.

-Keep in mind, this car was purchased for one purpose-get me back and forth to work-so I am already driving with mileage in mind, especially since I haven't paid for getting-back-and-forth-to-work gas in many years. I won't be hammering on it, and my driving style will remain consistent, so it should be very easy to tell what effect on MPG each maintenance activity will have. The only real variable that could affect this is the fact that summer is starting, so I'll be using the A/C. I'm guessing/hoping that this will be offset by the fact that I won't be using the defrost or letting the car idle for a few minutes during cold-weather warm-up as I have been.

-So, if interested in what comes of this, stay tuned. I'll be posting again after the plug/wires change, and will give the brand/part numbers at that time.
 

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2006 Forester X 2.5 AT Auto
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Discussion Starter #2 (Edited)
As I had hoped, the rain stopped this morning, and I was able to get the plugs and wires changed:

OUT-Denso PK16TT Platinum, age unknown, but the business end was pretty clean. These probably had some life left in them, but since I don't know when they were installed, hard to say.

IN-NGK BKR5EIX-11/5464 Iridium. $26.22 for a 4-pack on Amazon. Denso is a great plug, but NGK has never let me down, and I have used hundreds of them. Second favorite is Autolite, especially for V8 engines.

OUT-Belden Edge Premium 7mm wires. By the looks of them, probably an OK spark plug wire, but as I mentioned on previous posts, I have some brands that I am biased towards, and NGK is one of them. I love Taylor as well, but they don't list a set for my Forester.

IN: NGK RC-FX101/55004 8MM wires. $47.53 on amazon.

Initial observations from test drive:
-Engine does seem to start quicker? Maybe my imagination, but seems to.
-Clearly smoother idle. Never felt the engine idled roughly before, but is noticeably smoother, especially in gear at a light.
-Does seem to accelerate a bit quicker and smoother. Felt like it built power quicker on an entrance ramp.

Will post back two tanks from now with an MPG report.
 

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@Danspan -

Watch out for expectation bias...
Similar to the placebo effect, if you replace a part that you think will improve performance, you may observe improvement that is more a result of what you expect than an actual difference. Your comments like "seem to start quicker" and "smoother" are hard to quantify, but easy to imagine.

If a car has a problem that's corrected, there will likely be a difference that could be measured.
If you make a change that you think will improve mileage, your mileage may improve, but very minor changes in how you drive can dwarf any effects of changes from one functional component to another.

The point is that you can easily fool yourself into believing that something you did made a difference, where the actual difference is you.
It's all part of being a human, and there is a reason that sugar pills can cure an illness.... and they do.
In many medical studies, a sugar pill can improve the condition of 20% of the people who think they are given a new and effective drug.
It's the belief and what follows is self fulfilling prophesy.
 

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Discussion Starter #4
DragonSubie7,

I was looking forward to discussing technical things, not discussing the power of my subconscious, but here goes. Since this is an automotive forum, and not a peer-reviewed academic journal, I won't be entering into an argument about the placebo effect in general. I will, however, ask that you consider what I've already written, and what I will be reinforcing here, before continuing to suggest that any benefits to my work will simply be me willing my car into better MPG territory.

You wrote:

"Your comments like "seem to start quicker" and "smoother" are hard to quantify, but easy to imagine."

If you look at the context of what I wrote, you will see that I am already well aware about perception vs. reality, and opinion vs. a quantifiable sum. Since I didn't make a video of pre- vs. post staring, I was aware of the quicker starting being my own perception, since the observation could no longer be repeated, short of putting the old plugs and wires back in. Specifically, I felt that it was taking slightly fewer revs of the flywheel between turning the key and the engine starting. That's why I wrote, "Maybe my imagination". This was my way of conveying to the reader an admission to the possibility that something that I observed may not have happened the way I thought it did. So, as far as expectation bias, I'm on top of it. Also, I disagree that "smoother" is hard to quantify. I can look at my engine and see that it is idling smoother. I can put my hand on the intake runners and feel that it is idling smoother. I can also feel this through my steering wheel. I can hear that it is idling smoother. Finally, I can see that my tach needle is rock steady instead of slightly moving between marks. I clearly wrote that I wasn't expecting this, as I thought the idle was already pretty smooth for a high-mileage boxer engine.

You Wrote:

"If a car has a problem that's corrected, there will likely be a difference that could be measured."

You're right, I may be correcting actual problems as I go. I'm combining doing maintenance on a car that I have no maintenance records for, while simultaneously observing which maintenance actions may or may not improve mileage from an established baseline.

You wrote:

"If you make a change that you think will improve mileage, your mileage may improve, but very minor changes in how you drive can dwarf any effects of changes from one functional component to another.”

In the short term, I may agree with that. However, I disagree that my subconsciousness could maintain such an effect over the long-term. This will be a months-, if not year-long experiment. I leave work at that same time and arrive at the same time every day. If I subconsciously start hyper-mileage type driving, I will will notice immediately as I will likely be late for work. What you wrote also seems to indicate that maybe I expect everything I do to work. There is a degree of expectation, but only because my experience in knowing what is likely to work or not work spans decades and many vehicles (as mentioned in my OP). I've spent a lot of money in the past on what turned out to be bogus claims, and have fine-tuned the things I've found to work most often that not. This my first Subaru, so maybe what worked on an F-150 or a Plymouth 2.2 Turismo, or a Triumph TR7 won't work here. We'll see.

Since your last paragraph is a summary, I won't quote it here. My point is that I'm not refuting what you have to say about the placebo effect in general, but am offering a rebuttal to your assertion that I may be unduly vulnerable to the placebo effect and "self-fulfilling prophecy" in this case. I hope to show that my awareness of the situation was generally covered in my OP, and reinforced here. I further hope that I have assured you that although my ultimate goal is to attain the best possible MPG, my expectations, through doing this experiment many times, are neutral. At the end of the day, I want to see if I can find a way to spend less on gas in a high-mileage car, and if that pans out, to let others know how I did it.
 

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@Danspan -
I began my note with "Watch out for expectation bias... "
My point was that as a part of human nature, humans are by nature susceptible to it.
I never said you were "unduly vulnerable", as I don't know that and did not intend that, but it would be equally untrue for you to say you are immune to it.

It's great that you want to find out ways of getting better mileage... but consider this...
Auto manufacturers are desperate in their attempt to improve mileage in their fleets to meet government mandates.
If all it took was some different spark plugs, or any other commonly available accessory, why wouldn't they use them...
It's a rhetorical question.

What you may find are wear items that have affected your particular car's performance, and that might be improved by replacement.
Adding air to your tires when they are underinflated can make a huge difference. So does the weight you transport.
So does the number of stops you make, the traffic you do, or don't, encounter, the ambient temperature, the BTU's in your fuel blend, the wind velocity and direction, etc, etc, etc, etc...

In order to assign a result as to cause with your experiment, there are a lot of variables you cannot easily (and in many cases cannot at all) control.
MPG is a result. It is a measurable end product of all those input factors and by that is entirely dependent on them, which will make it difficult, if not impossible, to assign any particular value to a change you make, especially as you add changes as time goes on.


That being said, good luck.

In my case, I notice a dramatic improvement in mpg's just by slowing down.
 
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